The coloring components in conventional hair dye formulations are generally either substantive dyes or dyes which are formed from oxidation dye precursors of the primary intermediate and secondary intermediate type by oxidation with atmospheric oxygen or with other oxidizing agents (for example H2O2). For use in hair dye formations, the dyes are incorporated in a cosmetic carrier. The substantive dyes used are, for example, nitrophenylenediamine derivatives, anthraquinone derivatives or naphthoquinone derivatives.
The oxidation dyes used typically consist of a combination of a primary intermediate, for example a primary aromatic amine containing another free or substituted hydroxy or amino group in the para position or the ortho position, diaminopyridines, heterocyclic hydrazone derivatives, 4-aminopyrazolone derivatives or tetraaminopyridines, and a secondary intermediate, for example m-phenylenediamines, 3-aminophenols, resorcinols, naphthols, pyrazolones. These intermediates react in a coupling reaction in the presence of atmospheric oxygen or other oxidizing agents to form the actual dyes.
Good hair dye formulations are required above all to satisfy the following requirements. They must form the required color tone with sufficient intensity. In addition, they must be readily absorbed onto human hair without overly staining the scalp. The colors produced must be highly stable to heat, light, shampoos and the chemicals used for permanent waving. Finally, hair dye formulations must be toxicologically and dermatologically safe.
Accordingly, there is a constant need for hair dye formulations having improved toxicological and performance properties, more particularly in regard to the fastness of the hair colors produced.
It has now surprisingly been found that it is possible to improve the coloring properties of conventional hair dye formulations both of the primary and secondary intermediate type and also those based on substantive dyes.